Understanding Seasonal Weight Changes

Seasonal habits can shape your weight more than you might realise. While many people think weight gain happens only during major celebrations, this Australian research shows that small changes across the year can add up. These changes are normal, but learning how and why they occur can help you feel more confident and supported on your own weight management journey.

A world first study from the University of South Australia, funded by the NHMRC and published in JAMA Open Network, tracked how weight changed across a full twelve-month period. The findings showed clear patterns linked to holidays, weekends, and shifting seasons. The goal of the research was not to judge these patterns but to understand them, so that future support and education can be delivered at the right times.

One of the strongest trends found in the study was holiday related weight gain. During Easter, weight increased by about 0.29 percent, which is roughly 244 grams. During Christmas and New Year, weight rose by about 0.65 percent, which is approximately 546 grams. These modest changes are common and expected because celebrations usually bring more social meals, shared foods, and shifts in daily routines.

The study also found a weekly cycle. Most people naturally lose a small amount of weight during the week and gain it back on weekends. In total, this pattern results in a weekly fluctuation of around 0.3 percent or about 252 grams. This reflects how lifestyle changes across the week, such as eating out, relaxing, or social events, can influence weight in small ways over time.

The seasonal pattern was also unique. Unlike people in the Northern Hemisphere, whose weight generally rises in winter and falls in summer, Australians showed a twice-yearly cycle. Participants were heaviest in summer and lightest in autumn. Weight then increased again during winter and early spring before dipping at the end of spring. This cycle showed a difference of about 0.27 percent when comparing spring to summer.

Researchers noted that these patterns resemble yo yo style weight cycling when repeated year after year. While each fluctuation is small, the long term effect can contribute to gradual weight gain over time. Professor Carol Maher, the lead researcher, explained that understanding these predictable weight spikes could help guide future education and support programs, especially during higher risk times such as Christmas and winter. She also highlighted that two out of three Australian adults live with overweight or obesity, making this research increasingly important.

Importantly, these fluctuations are not a sign of failure. They are normal responses to lifestyle changes, seasonal routines, and cultural habits. The value of this research is in helping people understand that weight naturally shifts and that planning ahead for these predictable periods can make long term management feel easier and more achievable.

For many people, a healthy approach to weight involves more than one tool. Nutrition, physical activity, psychological support, medical care, and in some cases surgery or medication, all play different roles. Understanding how your environment and routine influence your habits is another helpful layer. It can guide you to make small choices that feel realistic and positive, rather than restrictive.

Practical steps might include setting gentle routines during busy social months, planning balanced meals ahead of celebrations, making time for movement when the weather changes, and seeking support when motivation dips. These strategies are not about avoiding enjoyment. They are about giving yourself structure and confidence so that you can participate in social events without stress or guilt.

Seasonal weight change is common and expected. With the right information and support, you can navigate each part of the year with more awareness and a plan that suits your lifestyle and health goals. This research offers new insight into when weight is most likely to shift and opens the door for targeted guidance that helps people feel more supported all year round.

If you would like support with managing these seasonal changes in a practical and sustainable way, our team is here to help. For anyone who wants to explore the research further, the full University of South Australia study is available here.